Wireless Power Transfer Foreign Object Detection via Switching Frequency
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Solution Overview
Problem
Foreign objects, such as metal or magnetic materials, between the transmission and reception coils in wireless power transfer systems can disrupt the magnetic field and cause abnormal operations, leading to system instability and temperature issues.
Innovation Solution
A method for detecting foreign objects using zero phase angle control for power transfer converters, which involves monitoring the change rate of the moving average of the switching frequency or input current to determine if a foreign object is present, and controlling the system to stop power transfer if deviations exceed a threshold.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If foreign object detection is implemented using additional sensors or detectors, then detection precision is improved, but device complexity increases
Solution Approach 1:
The system uses its own existing operational parameters (switching frequency and input current) for foreign object detection, rather than adding separate detection hardware. The controller analyzes variations in parameters already being monitored for power transfer control, making the existing system serve the dual purpose of power transfer and foreign object detection.
Solution Approach 2:
The controller is designed to perform multiple functions: it simultaneously controls the power transfer process and detects foreign objects by analyzing the same operational parameters. This multi-functionality eliminates the need for dedicated detection hardware while maintaining detection capability.
2Reliability
If foreign object detection is implemented using additional sensors, then reliability is improved, but device complexity increases
Solution Approach 1:
The system monitors its own operational characteristics to detect foreign objects, using the power transfer process itself as the detection mechanism. This self-monitoring approach improves reliability without adding independent detection systems.
Solution Approach 2:
The controller continuously monitors switching frequency and input current parameters and uses feedback from these measurements to detect foreign objects. When abnormal variations are detected, the system can stop power transfer to prevent unsafe operation, improving overall system reliability.
3Object-affected harmful factors
If the system stops power transfer when foreign objects are detected, then harmful factors are reduced, but productivity decreases
Solution Approach 1:
The system performs foreign object detection continuously during the power transfer process and stops power transfer in advance before foreign objects can cause harmful effects such as overheating or system instability. This preventive approach minimizes damage while maintaining charging efficiency by only interrupting when necessary.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables the detection of foreign objects without additional hardware, ensuring safe and stable operation of wireless power transfer systems by preventing disruptions and maintaining system stability.
Implementation Method 1
a magnetic induction type of the WPT system uses an electromagnetic induction phenomenon between a transmission coil in the GA and a reception coil in a vehicle assembly to transfer electric power
Implementation Method 2
the reception coil in the VA mounted on the EV makes an inductive resonance coupling with the transmission coil in the GA located in the charging station or the charging spot, and charges the battery in the EV using power transferred from the GA through the inductive resonance coupling
Data Source
AI summary
A method for detecting a foreign object between a transmission pad and a reception pad for wireless power transfer (WPT) may comprise steps of performing a zero phase angle (ZPA) control for a power transfer converter included in or connected to the transmission pad; detecting a characteristic parameter with respect to at least one of an input current and a switching frequency of the power transfer converter; and determining whether or not a foreign object exists between the transmission pad and the reception pad according to whether the characteristic parameter with respect to at least one of the input current and the switching frequency deviates from an allowable range.